In recent years a number of processes for expanding tobacco have been disclosed which involve rapidly heating tobacco that has been previously impregnated with an expansion agent. The expansion agents which have been proposed are organic or inorganic materials capable of rapid vaporization, expansive decomposition or other expansion under the heating conditions employed. The rapid formation and/or expansion of vapors or gases emanating from the expansion agent present in the tobacco is dependent in part on the rate of heating the impregnated tobacco. The rate of heating is, in turn, determined by the impregnant and moisture content of the tobacco, the temperature and heat capacity of the heating medium, the relative quantities of flow rates of the impregnated tobacco and heating medium, and the efficiency of the heat transfer between the heating medium and the impregnated tobacco.